1. Field of the Invention
The present invention relates to an image processing apparatus and method which can output a color image by performing predetermined image processing for input image data.
2. Background of the Invention
FIG. 11 is a block diagram showing an example of the arrangement of a conventional color image processing apparatus. The operation of the conventional color image processing apparatus will be described below with reference to FIG. 11.
Referring to FIG. 11, reference numeral 101 denotes an image sensing device such as a CCD or the like which outputs red, green, and blue (to be respectively referred to as R, G, and B hereinafter) analog signals by scanning an original; 102, an A/D converter for converting the analog signals output from the image sensing device 101 into corresponding digital signals; and 1001, a luminance/density conversion processing unit for performing luminance/density conversion processing for the R, G, and B image data output from the A/D converter 102 and outputting cyan, magenta, and yellow (to be respectively referred to as C, M, and Y hereinafter) signals.
Reference numeral 1002 denotes a masking processing unit for performing masking processing for the image data output from the luminance/density conversion processing unit 1001; 1003, a density correction processing unit for performing density correction processing for the image data output from the masking processing unit 1002; 1004, a magnifying processing unit for performing magnifying processing for the image data output from the density correction processing unit 1003; and 1005, an error diffusion processing unit for converting the multivalued C, M, and Y image data output from the magnifying processing unit 1004 into binary C, M, and Y signals by performing error diffusion processing for the multivalued data.
Reference numeral 105 denotes an ink-jet printer for printing out the image represented by the binary C, M, and Y signals output from the error diffusion processing unit 1005; 106, a CPU for controlling the respective components of this color image processing apparatus; 107, a RAM connected to the CPU 106 and used as a work area; and 108, a ROM connected to the CPU 106 and used to store instruction codes representing the procedure of processing executed by the CPU 106.
FIG. 12 is a flow chart showing the procedure of the color copying operation of the conventional color image processing apparatus having the arrangement shown in FIG. 11. The conventional color copying operation will be described below with reference to FIG. 12.
First of all, the image sensing device 101 scans an original to output analog signals (step S1101). The A/D converter 102 then converts the analog signals into digital signals (step S1102). The image data converted into the digital signals are subjected to conversion from R, G, and B luminance signals into C, M, and Y density signals (step S1103). This luminance/density conversion is performed for each color by looking up a table. FIG. 5 shows general characteristics stored in the table. Referring to FIG. 5, the abscissa represents the input luminance level; and the ordinate, the output density level.
Subsequently, the image data having a color space complying with the characteristics of the image sensing device are converted into data having a color space complying with the characteristics of the ink-jet printer by masking processing (step S1104).
If C, M, and Y data respectively represent input image values, and Cxe2x80x2, Mxe2x80x2, and Yxe2x80x2 data respectively represent output image values, a computation for masking processing is performed according to the following equation:                               (                                                                      C                  xe2x80x2                                                                                                      M                  xe2x80x2                                                                                                      Y                  xe2x80x2                                                              )                =                              (                                                                                a                    11                                                                                        a                    12                                                                                        a                    13                                                                                                                    a                    21                                                                                        a                    22                                                                                        a                    23                                                                                                                    a                    31                                                                                        a                    32                                                                                        a                    33                                                                        )                    xc3x97                      (                                                            C                                                                              M                                                                              Y                                                      )                                              (        1        )            
In addition, to comply with the characteristics of the ink-jet printer 105, density correction processing is performed for each of the colors, C, M, and Y, by looking up a table (step S1105). FIG. 6 shows general characteristics stored in the table. Referring to FIG. 6, the abscissa represents the input level; and the ordinate, the output level. The resultant data are subjected to magnifying processing to be converted from the resolution of the image sensing device 101 into the resolution of the ink-jet printer 105 (step S1106). If, for example, the resolution of the image sensing device 101 is 300 dpi, and the resolution of the ink-jet printer 105 is 720 dpi, the data is magnified 2.4xc3x97.
Linear interpolation used for this magnifying processing will be described below.
FIG. 4 shows the relationship between pixels before conversion and a pixel after conversion in the linear interpolation method. Referring to FIG. 4, pixels V, W, X, and Y are the pixels before conversion, and the luminance levels of the respective pixels are represented by v, w, x, and y. A pixel P is the pixel after conversion. The positional relationship between the pixel P and the pixels before conversion is set such that the pixel P is located at a distance La from the pixel V and a distance Lb from the pixel W in the main scanning direction (horizontal direction in FIG. 4), and is also located at a distance Ka from the pixel V and a distance Kb from the pixel X in the sub-scanning direction (vertical direction in FIG. 4). A luminance level p of the pixel P in FIG. 4 is therefore given by:                     p        =                                            v              xc3x97              Lb              xc3x97              Kb                        +                          w              xc3x97              La              xc3x97              Kb                        +                          x              xc3x97              Lb              xc3x97              Ka                        +                          y              xc3x97              La              xc3x97              Ka                                                          (                              La                +                Lb                            )                        xc3x97                          (                              Ka                +                Kb                            )                                                          (        2        )            
The multivalued C, M, and Y signals are converted into binary signals by an error diffusion process to be output from the ink-jet printer 105 (step S1107). Finally, the binary C, M, and Y signals are output from the ink-jet printer 105 (step S1108), and the color copying operation of this color image processing apparatus is ended.
As a technique of implementing the above prior art, a technique of performing all color image processes by hardware may be used. In this case, however, the hardware size becomes large, and the hardware cost becomes high.
As another technique, a technique of performing the above color image processing by software may be used. In this case, however, the image processing speed is low.
The present invention has been made in consideration of the above prior art, and has as its object to provide an image processing apparatus and method which can perform both image processing and image printing processing at high speeds.
To achieve the above object, one preferred embodiment of the present invention discloses an image processing apparatus comprising: white region determination means for determining the presence/absence of a white region in an image represented by image data to be processed; image processing means for performing image processing while executing different processes for a region determined as a white region by the white region determination means and a region other than the white region; and printout means for printing out an image processed by the image processing means, the printout means printing out the image while skipping the white region.
It is another object of the present invention to provide an image processing apparatus and method which can perform image processing and image printing processing at high speeds.
To achieve the above object, one preferred embodiment of the present invention discloses an image processing apparatus for performing image processing for input image data and causing predetermined print means to perform print processing, comprising: determination means for determining the presence/absence of a white region in an image represented by the input image data in units of predetermined unit regions; control means for omitting execution of at least one of general image processes for a region determined as a white region by the determination means; and output means for outputting, to the predetermined print means, information indicating that execution of the image process is omitted by the control means.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.